Heating system

ABSTRACT

A heating system including a spark ignitor for a pilot burner which utilizes a safety shut off valve operated by the pilot thermocouple when the pilot goes out, wherein the ignitor is connected in parallel with the thermostat. If an air or gas disturbance causes the pilot to go out, the same disturbance or a temporary electric power failure may prevent or delay pilot reignition. If the safety valve closed before reignition, no hazard exists. However, if the safety valve is still open while initially no reignition occurs, the thermostat opens the main valve and reignition is thus prevented for a relatively long time, e.g., several seconds, a large amount of gas can be dumped into the combustion chamber, mixed with air therein and exploded by delayed ignition. In the unique hook-up where the ignitor is connected in parallel with the thermostat, no delayed ignition can take place. If the pilot has not been reignited prior to the thermostat switch closing, i.e., calling for heat, the ignitor will be disabled by the thermostat switch thus preventing ignition.

United States Patent Loklrart 45 Dec. 5, 1972 [54] HEATING SYSTEM [72]Inventor: Hendricus Johannes Lokkart, Ar-

leta, Calif.

[73] Assignee: International Telephone and Telegraph CorporatiomNewYork, NY.

[22] Filed: March 25, 1971 [21] Appl. No.: 127,884

[52] US. Cl ..431/43, 431/53 {51] Int. Cl ..F23q 9/08 [58] Field ofSearch ..431/43, 45, 46, 47, 53;

[56] References Cited 7 UNITED STATES PATENTS [5 7] ABSTRACT A heatingsystem including a spark ignitor for a pilot burner whichutilizes asafety shut off valve operated by the pilot thermocouple when the pilotgoes out, wherein the ignitor is connected in parallel with thethermostat. If an air or gas disturbance causes the pilot to go out, thesame disturbance or a temporary electric power failure may prevent ordelay pilot reignition. If the safety valve closed before reignition, nohazard exists. However, if thesafety valve is still open while initiallyno reignition occurs, the thermostat opens the main valve and reignitionis thus prevented for a relatively long time, e.g., several seconds, alarge amount of gas can be dumped into the combustion chamber, mixedwith air therein and exploded by delayed ignition. In the unique hook-upwhere the ignitor is connected in parallel with the thermostat, nodelayed ignition can take place. If the pilot has not been reignitedprior to the thermostat switch closing, i.e., calling for heat, theignitor will be disabled by the thermostat switch thus preventingignition.

5 Claims, 2 Drawing Figures /6N/TOR. 2P

- HEATING SYSTEM BACKGROUND OF THE INVENTION I This invention relates tofuel burning apparatus, and more particularly, to a safety shut offforan electrical pilot ignitor.

In a conventional heating system, an electromagnetic safety valve isenergized by a thermocouple heated by, for example, a natural gas pilot.The gas inlet is connected first to the safety valve. Closure of thesafety valve thus prevents gas from entering any part of the system. Solong as the pilot is burning and keeps the thermocouple up totemperature, the safety valve is maintained open. If the pilot goes out,the safety valve closes after a time delay dependent upon the rate ofcooling of the thermocouple.

By themselves, spark ignitors are old in the art. It is also old in theart to use a spark ignitor to light the pilot of a heating system.However, during the said time delay the safety valve is open.Conventional spark ignitors spark at regular intervals during actuation.However, if the same disturbance that caused pilot outage persists,reignition may be delayed. Thus, several seconds before reignition,great quantities of gas can escape from the main burner while the pilotis put. Subsequent reignition of this gas mixed with air in thecombustion chamber can thereby cause an explosion that is In accordancewith the system of the present invention, the above-described and otherdisadvantages of the prior art are overcome by employing an electricalignitor for the pilot of a heating system, the ignitor having a powerinput circuit connected in parallel'with the system thermostat circuit.

The thermostat circuit includes a series connected switch which, whenclosed, shunts the ignitor input and renders it inoperative. The sameswitch, when closed, may also open the main gas valve. However, with theignitor rendered inoperative, the hazard due to the escape of gas issubstantially lessened. I

The above-described and other advantages of the present invention willbe better understood from the following detailed description whenconsidered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In. the drawings which are to beregarded as merely illustrative:

FIG. 1 is a diagrammatic view of a heating system; and

FIG. 2 is a schematic diagram of a portion of the heating system shownin FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawing in FIG. 1, a gasinlet is connected to the'inlet of an electromagnetic safety valve 11.As gas line 12 connects the outlet of valve 11 with the inlet of amanual gas valve 47. The outlet of manual gas valve 47 is connected tothe inlet ofa main gas valve 13. A gas line 14 connects the outlet ofvalve 13 with the main burner 15 of the system.

' input leads 26 and 27;

A pilot burner is indicated at 16. A gas pipeline 17 forms a pipe T withline 12 and connects the same to pilot burner 16. I

A thermocouple 18 is positioned adjacent pilot burner 16 to be heated bythe burning gas over pilot burner 16. Thermocouple 18 has electricaloutput leads l9 and 20 which are. connected to valve 1 1. Whenthermocouple 18 is up to temperature, and the gas escaping from pilotburner 16 is ignited, valve 11 will stay open. If the pilot light goesout, thermocouple will cool. However, valve 11 will not closeimmediately. Specifically, there will be a time delay between when thepilot goes out and when valve 1 l closes.

A spark ignitor 21 has contacts 22 and 23 from the output thereof tospark electrodes 24 and 25, respectively, positioned over pilot burner16. Ignitor 21 may be of the spark type for automatically igniting thepilot only when it goes out. Alternatively, ignitor 21 may be of thespark type that produces sparks at regular intervals independently ofpilot outage. Ignitor 21 has power As stated previously, ignitor 21 maytake any one of a great many forms. However, as an example only, ignitor21 may beof the type disclosed in copending application Ser. No. 77,070filed Oct. 1, 1970, and now U.S. Pat. No. 3,662,185 for SPARK GENERATORAND COMPONENTS THEREFOR by Said Sapir, assignor to the assignee of thepresent application. Said applica tion, in its entirety, is herebyincorporated herein by this reference hereto as though fully set forthherein hereat.

Whatever ignition apparatus is employed will generally have an inputresistance which is large in comparison to the resistance of winding 35.Stated other ways,.circuit 37 in relation to ignitor 21 must have aresistance low enough to disable it by creating effectively, a shortcircuit between leads .26 and 27 when switch 39 is closed. Further, theinput resistance of ignitor 21 must be sufficiently large so as toprevent sufficient energization of winding 35 to open main valve 13 whenswitch 39 is open. Still further, the parallel resistance of circuit 37with the ignitor input resistance must be sufficiently low when switch39 is closed so as to energize winding 35 enough to open main valve 13.

In FIG. 2, an input transformer 28 is shown having a volt primary 29, a24 volt secondary 30 and a magnetic core 31.

Secondary 30 has a lead 32 connected to one end thereof, and a lead 33connected to the other end thereof. I

Also shown in FIG. 2 is a thermostat 34, the solenoid winding 35 of maingas valve 13 and spark ignitor 21.

Thermostat 34 includesa spiral bimetal 36 and a series circuit 37including a resistive heater winding 38 and a switch 39 connected inseries therewith. Winding 38 called an anticipator and heats the bimetal36 when switch 39 is closed to prevent the space to be heated fromgetting too hot before switch 39 opens. Bimetal 36 operates switch 39.

Circuit 37 has leads 40 and 41 extending therefrom, Thermostat 34, withleads 40 and 41 disconnected from the circuit shown in FIG. 2, byitself, may be entirely conventional. The same is true of ignitor 21when input leads 26 and 27 thereto are disconnected from the circuit ofFIG. 2, and the same is true of winding 35 of gas valve 13 when itsleads 42 and 43 are disconnected from the circuit of FIG. 2. 7

As shown, leads 26, 32 and 40 are connected to a common junction 44.Leads 27, 41 and 42 are connected to a common junction 45. Leads 33 and43 are connected together.

OPERATION Whensafety valve 1 1 is closed and the system is cold, as isconventional, safety valve 11 may be opened manually by depressing a pin46 shown in FIG. 1. The pilot may then be lit manually and pin 46depressed for a length of time to heat thermocouple 18 up totemperature. The voltage appearing between thermocouple leads 19 and 20will then hold safety valve 11 open without depressing pin 46 anylonger. Pin 46 may be spring biased upwardly, as viewed in FIG. 1.-

Manual gas valve 47 may then be opened, and the system can be controlledby thermostat 34 located in a space to be heated by main burner 15.

Should the pilot go out, ignitor 21 will attempt to relight the pilot.If thermostat 34 is not calling for heat, switch 39 will be open, andthe voltage drop across winding 35 will not be suflicient to disableignitor 21. Further, the voltage drop across winding 35 will beinsufficient to open main valve 13. Main valve 13 will thus remainclosed. 7

If the temperature of thermostat 34 is of a certain value, switch 39 mayclose. When switch 39 is closed, the resistance of circuit 37, which isthen connected in parallel with the power input circuit of ignitor 21,is sufficiently low so as to render ignitor 21 inoperative. That is, theoutput voltage therefrom is insufficient to produce ignition.

Note will be taken that closure of switch 39 will cause winding 35 to beenergized. This means that main gas valve 13 will be opened and gas canescape from main burner 15.

Were spark ignitor input leads 26 and 27 disconnected from leads 40 and41 and reconnected directly to transformer leads 32 and 33, a hazardouscondition could exist. In such a case, if the pilot light went out wouldnot reignite because of the same persisting condition that caused theinitial outage, closure of thermostat switch 39 would energize winding35, open main valve 13 and cause a large amount of gas to be built up inthe combustion chamber before the safety valve 11 would shut off. Laterreignition of the said large amount of gas could then cause anexplosion.

The said hazardous condition is avoided in accordance with the device ofthe present invention because thermostat 34 which energizes solenoid 35by the closure of switch 39 also disables the ignitor by the self sameswitch closure. Thus, even through the main valve 13 has been opened bythe switch closure the gas admitted to the main burner by the main valve13 cannot explode because the disabled ignitor 21 cannot ignite the saidgas so admitted.

Note will be taken that even though the closure of switch 39 creates ahazard by energizing main valve winding 35, the very same switch 39minimizes this hazard by shunting the power input circuit of ignitor 21.

Note will be taken that the system of the present invention is by nomeans limited to a spark ignitor or to an ignitor with two sparkelectrodes. For example, it is conventional to use three sparkelectrodes or only one.

- That is, a spark may be produced between a high voltage electrode and,for example, a pilot shield which is grounded when the ignitor has aground connection.

By this reference hereto, said application Ser. No. 77,070 is herebyincorporated herein as though fully set forth herein hereat.

By this reference hereto, corrected US. Pat. No. 3,303,866 is alsohereby incorporated herein as though fully set forth herein hereat. Saidpatent may be substituted for the entire structure shown in FIG. 1,except for leads 22, 23, 26 and 27; spark electrodes 24 and 25; andignitor 21.

The system of the present invention is by no means limited to anyparticular voltage such as 24 volts.

What is claimed is:

1. A heating system comprising: an inlet; a main burner; anelectromagnetic safety valve having an inlet and an outlet; a mainsolenoid valve, said safety valve and said'main valve being connected inthat order to said main burner to admit gas to said main burner onlywhen both of said valves are open; a pilot burner connected from theoutlet of said safety valve to receive combustible fuel therefrom whensaid safety valve is open; a thermocouple positioned adjacent said pilotburner to be heated when fuel escaping from said pilot burner isignited; means electrically connecting said thermocouple to said safetyvalve, said thermocouple supplying an operating voltage to said safetyvalve suflicient to hold said safety valve open when the fuel escapingfrom said pilot burner is ignited for a sufficient length of time, saidsafety valve being adapted to close at a time after the pilot light hasgone out; an electrical ignitor having ignition means connected to theoutput thereof and extending contiguous to said pilot burner forignition of fuel escaping therefrom, said ignitor. having first andsecond leads; first and second main leads; and a thermostat positionedin a space to be heated by said main burner and including a seriescircuit, said circuit including a series connected switch, saidthermostat including a temperature sensitive device to close said switchwhen the ambient temperature falls below a set temperature and to opensaid switch when the ambient rises thereabove, said circuit having firstand second leads connected from each end thereof, said first main leadbeing connected to said first circuit lead and to said first ignitorlead, said main valve including a solenoid winding having a leadconnected from each end thereof, said second circuit lead beingconnected to said second ignitor lead and to one of said winding leads,said second main lead being connected to the other of said windingleads, said circuit having a resistance such that closure of said switchrenders said ignitor inoperative, said ignitor being operative when saidswitch is open, said ignitor having an input resistance sufficientlylarge to prevent sufficient energization of said solenoid winding toopen said main valve when said switch is open, the resistance of theparallel connection of said circuit and the ignitor input when saidswitch is closed to cause sufficient energization of said solenoidwinding to open said main valve.

2. The invention as defined in claim 1, wherein said ignitor is a sparkignitor which produces a spark at said pilot burner with a predeterminedfrequency when the pilot light is out, said ignition means including atleast two spaced spark electrodes.

3. The invention as defined in claim 2, wherein said circuit includes aheat anticipator, said heat anticipator being a resistive heaterpositioned to heat said temperature sensitive device and connected inseries with said switch.

4. The invention as defined in claim 3, including a said main valve.

5. The invention as defined in claim 1, wherein said circuit includes aheat anticipator said heat anticipator being a resistive heaterpositioned to heat said temperature sensitive device and connected inseries with said switch.

1. A heating system comprising: an inlet; a main burner; anelectromagnetic safety valve having an inlet and an outlet; a mainsolenoid valve, saiD safety valve and said main valve being connected inthat order to said main burner to admit gas to said main burner onlywhen both of said valves are open; a pilot burner connected from theoutlet of said safety valve to receive combustible fuel therefrom whensaid safety valve is open; a thermocouple positioned adjacent said pilotburner to be heated when fuel escaping from said pilot burner isignited; means electrically connecting said thermocouple to said safetyvalve, said thermocouple supplying an operating voltage to said safetyvalve sufficient to hold said safety valve open when the fuel escapingfrom said pilot burner is ignited for a sufficient length of time, saidsafety valve being adapted to close at a time after the pilot light hasgone out; an electrical ignitor having ignition means connected to theoutput thereof and extending contiguous to said pilot burner forignition of fuel escaping therefrom, said ignitor having first andsecond leads; first and second main leads; and a thermostat positionedin a space to be heated by said main burner and including a seriescircuit, said circuit including a series connected switch, saidthermostat including a temperature sensitive device to close said switchwhen the ambient temperature falls below a set temperature and to opensaid switch when the ambient rises thereabove, said circuit having firstand second leads connected from each end thereof, said first main leadbeing connected to said first circuit lead and to said first ignitorlead, said main valve including a solenoid winding having a leadconnected from each end thereof, said second circuit lead beingconnected to said second ignitor lead and to one of said winding leads,said second main lead being connected to the other of said windingleads, said circuit having a resistance such that closure of said switchrenders said ignitor inoperative, said ignitor being operative when saidswitch is open, said ignitor having an input resistance sufficientlylarge to prevent sufficient energization of said solenoid winding toopen said main valve when said switch is open, the resistance of theparallel connection of said circuit and the ignitor input when saidswitch is closed to cause sufficient energization of said solenoidwinding to open said main valve.
 2. The invention as defined in claim 1,wherein said ignitor is a spark ignitor which produces a spark at saidpilot burner with a predetermined frequency when the pilot light is out,said ignition means including at least two spaced spark electrodes. 3.The invention as defined in claim 2, wherein said circuit includes aheat anticipator, said heat anticipator being a resistive heaterpositioned to heat said temperature sensitive device and connected inseries with said switch.
 4. The invention as defined in claim 3,including a conduit connecting the outlet of said safety valve with saidpilot burner, and a manually operable valve connecting the outlet ofsaid safety valve with the inlet of said main valve.
 5. The invention asdefined in claim 1, wherein said circuit includes a heat anticipator,said heat anticipator being a resistive heater positioned to heat saidtemperature sensitive device and connected in series with said switch.